Magnetostrictive ink jet



1, 1967 R. A. ADAMS 3,334,350

MAGNETOSTRICTI VE INK JET Filed Aug. 19, 1964 \6 Mg 0 ELECTRO- MECHANICAL 24 \N\ RANSDUCER UNDER \/\DEO PRESSURE SlGNAL SGURCE l I I '7. 1

PRIOR ART F\ELD DOTENTMAL SOURCE H\GH FREQUENCY SOURCE lNl/ENTOQ fee/144m A. ADAMS BYMW United States Patent 3,334,350 MAGNETOSTRICTIVE INK JET Roman A. Adams, Skokie, Ill., assignor to The A. B. Dick Company, Chicago, 11]., a corporation of Illinois Filed Aug. 19, 1964, Ser. No. 390,696 5 Claims. (Cl. 346-75) This invention relates to apparatus for producing the information represented by video signals using ink drops deposited on a writing medium, and more particularly, to improvements therein.

The-re has been developed apparatus for making a record of a writing medium of the information represented by video signals by generating a stream of ink drops and then deflecting these ink drops which are directed toward a writing medium, using video signals, in a manner so that when the ink drops do reach the writing medium they represent the information contained in the video signals. The apparatus which is employed for producing the ink drops consists of an ink reservoir in which there is ink under pressure. The ink reservoir feeds a pipe which is connected to a nozzle. An electromechanical transducer is employed to vibrate the nozzle at some suitable hgh frequency. The ink accordingly is ejected from the nozzle in a stream which shortly thereafter breaks into individual drops.

Because these drops are to be charged and thereafter deflected by electrical signals, it is desirable to make these drops have as uniform a size as possible. It is also desirable to form these drops with a close spacing, since the closer the spacing, the better the resolution which can be obtained. Also, it is desirable to form the drops into a small size so that the amplitude of the signals required to deflect them should not become excessive. Constructions presently used for forming the ink drops comprises a metal nozzle which is vibrated by means of a separate electromagnetic transducer. This has not provided a satisfactory drop size or uniformity or close spacing of the drops.

An object of this invention is to provide a unique drop forming structure.

Another object of this invention is to provide a drop forming structure which allows drops to be formed uniformly and closely spaced to one another.

Still another object of the present invention is the provision of an ink drop forming structure which is easy to manufacture and relatively inexpensive to build.

These and other objects of the invention may be achieved by constructing terminating portions of the ink drop forming tube out of magnetostrictive tubing around which a coil is wrapped. In the output end of the tubing, a watch jewel bearing is fitted or glued into place. The ends of the coil or winding around the tubing have a high frequency signal applied thereto in response to which the tubing elongates and contracts whereby the ink drop stream breaks down into discrete droplets, the number of which are related to the frequency of the high frequency source of excitation.

The novel features that are considered characteristic of this invention are set forth with particularity in the appended claims. The invention itself both as to its 0rganization and method of operation, as Well as additional objects and advantages thereof, will best be understood from the following description when read in connection with the accompanying drawings, in which:

FIGURE 1 is a schematic drawing of an arrangement for ink drop recording system in accordance with the prior art, and

FIGURE 2 illustrates ink drop forming apparatus in accordance with this invention.

In order to afford a better understanding of this invention, a schematic drawing of ink drop recording apparatus in accordance with the prior art is shown in FIG- URE 1 for the purpose of affording a better understanding of this invention. This apparatus comprises an ink reservoir 10 under pressure. Tubing 12 is connected to the ink reservoir 10 and terminates in a nozzle 14. An electromechanical transducer 16 vibrates the tubing and the nozzle in response to the output of the source of oscillation 18. The source of oscillation may be a source at a frequency which may vary from 5 kc. to kc.

The electromechanical transducer 16 is vibrated substantially at the frequency of the signal source, causing the tubing and nozzle to vibrate whereby the ink stream 20 soon breaks down into ink drops 22. A video signal source 24 which is synchronized by the source of oscillation is connected between the nozzle and a charging cylinder 26. As a result, each of the ink drops, which should be of substantially the same mass, receive a charge, the amplitude of which is determined by the amplitude of the video signal applied from the source 24 and the charging ring 26.

The charged ink drops, after passing through the charging ring, pass into a static electric field which is established between two plates respectively 30, 32, which are connected to a field potential source 34. As a result of the action between the field and the charge on each drop, the drops are deflected from their center line path between the plates in accordance with the charge which they carry. Thus, when they fall finally on a writing medium 36 which is moving past the plates, a mark occurs on the writing medium in ink representative of the information in the video signals.

From the foregoing brief description of the prior art arrangement, an appreciation should be had of the requirement for uniformity of drop spacing, small size for the drops, uniformity of drop size, as well as close spacing between the drops. FIGURE 2 shows an arrangement, in accordance with this invention, of drop forming apparatus which produced improved results over the prior art device. This comprises tubing, 40, which may be made out of magnetostrictive material, such as nickel. This tubing 40 may be attached to the tube 12 which is connected to the ink reservoir. A coil 42 is wound on a bobbin 46 which is inserted over the tubing 40 and held in place "by a clamp 48. The end of the thin wall tubing 40 is then flared to accept a jewel 50 with a hole therethrough. This jewel can be a watch hearing which is glued into place. The center opening of the jewel has a diameter on the order of 2.4 thousandths of an inch. These watch jewels are commercially available and are relatively inexpensive.

The coil is connected to a source of high frequency 52 which may range from 5 kc. to 85 kc., by way of example. 'I he varying magnetic field developed as a result of the excitation of the coil causes the magnetostrictive tubing to extend and contract at the same frequency. This breaks the flow of the liquid into discrete drops which are related to the frequency of the high frequency source. This construction enables the mass of the vibrating tube to be easily determined so that the device may be ope-rated at the resonant frequency of the system at which excellent operation and uniformity of results may be obtained.

There has accordingly been described and shown herein a novel, useful and unique construction for a device for forming ink drops.

What is claimed is 1. In nozzle apparatus to which ink is applied under pressure for the purpose of producing a succession of uniformly spaced substantially uniform ink drops, the improvement in said nozzle apparatus comprising a tube made of magnetostrictive material, means for applying said ink under pressure to one end of said tube, means mounted in the other end of said tube having an opening therein smaller than the internal diameter of said tube, for determining the diameter of the emitted ink stream, means for applying a varying magnetic field to said tube to vibrate said tube at the frequency of said varying magnetic field and to form drops from said emitted ink stream synchronously therewith.

2. In nozzle apparatus to which ink is applied under pressure for forming substantially uniformly sized and uniformly spaced ink drops, the improvement comprising a tube made of magnetostrictive material, drop siZe detenmining means having an opening therethrough smaller than the inner diameter of said tube for determining the size of the drops to be formed, means mounting said drop size determining means at one end of said tube, a coil winding surrounding said tube, and means for applying excitation at a desired frequency to said coil winding for causing said magnetostrictive tubing to vibrate responsive thereto whereby ink applied to the other end of said tubing passes therethrough and through the opening in said drop size deter-mining means to form a succession of uniformly spaced substantially uniformly sized drops.

3. Apparatus as recited in claim 2 wherein said magnetostrictive tubing is made of nickel.

4. Apparatus as recited in claim 2 wherein the mass of said magnetostrictive tubing is determined in accordance with the desired resonant frequency and the frequency of excitation of said means for exciting said winding at a desired frequency is that resonant frequency.-

5. Apparatus as decited in claim 2 wherein said drop size determining means is a Watch jewel bearing.

No references cited.

RICHARD B. WILKINSON, Primary Examiner. J. W. HARTARY, Assistant Examiner. 

1. IN NOZZLE APPARATUS TO WHICH INK IS APPLIED UNDER PRESSURE FOR THE PURPOSE OF PRODUCING A SUCCESSION OF UNIFORMLY SPACED SUBSTANTIALLY UNIFORM INK DROPS, THE IMPROVEMENT IN SAID NOZZLE APPARATUS COMPRISING A TUBE MADE OF MAGNETOSTRICTIVE MATERIAL, MEANS FOR APPLYING SAID INK UNDER PRESSURE TO ONE END OF SAID TUBE, MEANS MOUNTED IN THE OTHER END OF SAID TUBE HAVING AN OPENING THEREIN SMALLER THEN THE INTERNAL DIAMETER OF SAID TUBE, FOR DETERMINING THE DIAMETER OF THE EMITTED INK STREAM, MEANS FOR APPLYING A VARYING MAGNETIC FIELD TO SAID TUBE TO VIBRATE SAID TUBE AT THE FREQUENCY OF SAID VARYING MAGNETIC FIELD AND TO FORM DROPS SAID EMITTED INK STREAM SYNCHRONOUSLY THEREWITH. 